Actelion unveiled new data at the World Congress of Cardiology in Barcelona, Spain, showing that its endothelin antagonist Tracleer improved exercise capacity and WHO functional class in patients with Eisenmenger’s syndrome.

Although Eisenmenger’s syndrome - a form of pulmonary arterial hypertension – is uncommon, cases are expected to increase as more children with congenital heart disease survive to adulthood due to improved surgical techniques and treatments.

Tracleer (bosentan) is already approved to treat PAH and is on the way to becoming a blockbuster drug with sales in excess of $1 billion.

The study investigated 37 patients who were previously enrolled in the BREATHE-5 study. Treatment with bosentan improved exercise capacity (six minute walk test) and WHO functional class (over two thirds improved to functional class II). Observed improvements were sustained for up to six months after starting treatment.

According to Professor Michael Gatzoulis from the Royal Brompton Hospital in London, the results confirm the previous findings from BREATHE-5 in these difficult to treat patients.

“It is exciting and reassuring to see that the benefit in the double blind period was maintained over a prolonged period of time and that patients transferred from placebo to bosentan showed a rapid improvement in exercise capacity and functional class,” he said.

Bosentan is currently licensed for the treatment of pulmonary arterial hypertension to improve exercise capacity and symptoms in patients with WHO Class III PAH (in Europe).